Magnetic switch assembly for coding information

ABSTRACT

The present invention is directed to the improved mounting and disposition of a series of magnetic switching members utilized to convert the characters printed on a keyboard into coded electrical signals, generally wherein each switch is opened or closed in response to movement of each of a selected group of interposers which control printing of each character on the keyboard. Each of the magnetic switch elements is mounted on the back of a circuit board, and a magnetic switch-actuating member for each switch is releasably inserted in the slotted end of a holder which in turn is attached in close-fitting relation to an interposer so that the actuating member is securely but adjustably disposed for movement in response to movement of its interposer in closely spaced parallel relation to a switch.

United States Patent Siegel Mar. 14, 1972 [54] MAGNETIC SWITCH ASSEMBLYFOR CODING INFORMATION [72] Inventor: Martin Siegel, San Mateo, Calif.

[73] Assignee: Datel Corporation, Falls Church, Va.

[22] Filed: Jan. 21, 1969 21 Appl. No.: 792,470

Primary Examiner-Edgar S. Burr Attorney-.lohn E. Reilly [57] ABSTRACTThe present invention is directed to the improved mounting anddisposition of a series of magnetic switching members utilized toconvert the characters printed on a keyboard into coded electricalsignals, generally wherein each switch is opened or closed in responseto movement of each of a selected group of interposers which controlprinting of each character on the keyboard. Each of the magnetic switchelements is mounted on the back of a circuit board, and a magneticswitch-actuating member for each switch is releasably inserted in theslotted end of a holder which in turn is attached in close-fittingrelation to an interposer so that the actuating member is securely butadjustably disposed for movement in response to movement of itsinterposer in closely spaced parallel relation to a switch.

6 Claims, 5 Drawing Figures LOGIC CIRCUIT PATENTEUMAR 14 I972 SHEET 1 UF2 FIG: 5

INVENTOR.

S/EGEL ATTOR/V MARTIN BY/Z/ PAIENTEDMAR 14 I972 3, 648 8 l 7 sum 2 OF 2INVENTOR.

MARTIN SIEGEL A 7' TORNE Y5 MAGNETIC SWITCH ASSEMBLY FOR CODINGINFORMATION This invention relates to coding devices for businessmachines, and more particularly relates to a novel and improved meansfor converting information as it is typed or printed into codedelectrical signals for transmission to a recording unit.

It is customary to convert information as it is printed or typed by abusiness machine, such as, a keyboard printer unit, into codedelectrical signals and signal combinations representative of each itemof information printed, recording and signals produced, and thereaftertransmitting the signal back to the typewriter for automaticallyprinting the same matter as originally prepared, the objective being ofcourse to provide high speed, reliable reproduction of the information.A typical keyboard printer unit is that generally disclosed and setforth in US. Pat. No. 2,919,002 to L. E. Palmer or U.S. Pat. No.3,260,340 to H. C. Locklar et al., wherein the printer unit is providedwith a spherical print head bearing columns and rows of characters, eachcharacter being selectively advanced into position for printing byrotation and tilt of the print head in response to actuation of a keylever. The rotation and tilt of the print head are mechanicallycontrolled by a displacement mechanism which is actuated by linkage setin motion by depression of each key lever. The linkage broadly comprisesa character interposer movable in response to depression of each keylever to actuate one or more selector bails and latch interposers inpredetermined combinations representative of the key or character andwhich, through a series of selector latches in the displacementmechanism will determine the degree of rotation and tilt of the printhead. Thereafter the head is advanced to strike the platen to print thechosen character.

In a similar manner, series of electrical pulses or signals representingeach character or item of information may be transmitted back from aremote station, such as, a magnetic tape recording and playback unit toa series of electromagnets or solenoids associated with the latchinterposers. Each signal of a combination representing a character willenergize a sole noid and, through the latch interposers, will controlrotation and tilt of the print head to present the chosen character forprinting.

In converting the information into coded electrical signals forrecording or other purposes, it is highly desirable to provide anarrangement which is compact, can be quickly and easily installed and isreadily conformable and adjustable for use in different types ofbusiness machines. In accordance with the present invention, a magneticswitch assembly has been devised which will accomplish the foregoing andin a unique manner will closely and accurately follow movement of thecontrol linkage actuated for printing each character to generate acombination of electrical pulses or signals representative of eachcharacter or unit of information.

It is therefore an object of the present invention to provide a noveland improved coding device particularly adaptable for convertingcharacters as they are printed or typed into electrical signals fortransmission to another recording unit; and further to provide a deviceof the character described which is compact and comprises a minimumnumber of parts so as to permit its mounting and disposition directlybetween the control linkage and the control circuitry of the printerunit.

It is another object of the present invention to provide a magneticswitch assembly for coding information printed by means of a keyboardprinter unit wherein the assembly is readily attachable to anddetachable from the printer control linkage and a circuit mounting boardso as 'to be readily conformable for use with different types oftypewriter printer units, and can be easily adjusted and serviced oncein place; and more specifically to provide a magnetic switch assembly inwhich a series of switching elements are selectively controlled by acorresponding number of magnetic actuating members adjustably insertablein holders attached to the control linkage to produce coded electricalsignals in different combinations representative of each characterprinted.

It is a still further object of the present invention to provide for anovel and improved magnetic switch assembly wherein reed switch elementsare positioned on the back of the printed circuit board, each element tobe actuated in direct response to movement of a magnetic actuatingmember releasably inserted in a holder to follow movement of controllinkage members in a printer unit for producing electrical signals orpulses for transmission in combinations representative of each charactermanually selected for printing.

In the magnetic switch assembly of the present invention, each of aseries of magnetically responsive switch elements is mounted on the backof a circuit board in facing relation to each latch interposer orequivalent linkage arm in the keyboard unit which controls movement ofthe print element. A magnetic actuating member for each of the switchelements is releasably inserted laterally in the forwardly divergentslotted end of a holder projecting from each of the latch interposerstoward an aligned switch element. Each holder is connected to aninterposer by snap-fitting insertion of the interposer into a recess atthe end of the holder opposite to the slotted end. The actuating memberis positively held against lateral release but is axially adjustable inthe slotted end with the sides of the slotted end flanking the sides ofthe switch element; and upon movement of the interposer the actuatingmember will axially advance in closely spaced parallel relation to theswitch either to effect opening or closing of the switch. In this way, aselected combination of switches will be actuated when a correspondingcombination of interposers is advanced to print a particular characterand which actuation may be utilized to generate coded electrical signalsfor transmission to another station.

The above and other objects, advantages and features of the presentinvention will become more readily appreciated and understood from aconsideration of the following detailed description when taken togetherwith the accompanying drawings, in which:

FIG. 1 is a perspective view illustrating parts of a conventionalkeyboard printer unit.

FIG. 2 is a perspective view from the underside of th printer unit shownin FIG. 1 illustrating the relative disposition and arrangement of apreferred form of magnetic switch assembly.

FIG. 3 is an elevational view of a series of switching elements mountedon a printed circuit board.

FIG. 4 is a top view in detail of the preferred form of one of themagnetic switches in the switch assembly in accordance with the presentinvention; and

FIG. 5 is a sectional view taken about line 55 of FIG. 4.

Referring in detail to the drawings, in FIG. I a conventional printerunit has a spherical print head 10 provided with rows and columns ofcharacters, not shown, to be selectively advanced into position forprinting by means of a displacement mechanism which is actuated inresponse to depression of each of a plurality of key levers, one suchkey lever being designated at 12 for movement about a shaft 13. Whenevera key lever 12 is depressed by its key button 15, a pawl 16 on key lever12 engages a character interposer 17 to slidably advance the interposerand in turn to cause movement of selector balls 20, the latter beingdisposed for engagement by lugs 21 on the character interposer. Eachcharacter interposer has a different lug spacing so that differentcombinations of selector bails are advanced in response to depression ofeach key lever; and each combination of any one or more of the selectorbails so advanced by a key lever is representative of the characterdisplayed on the related key button. Each of the selector bails willcontrol movement of an associated latch interposer 24, and of the latchinterposers shown in FIGS. 1 and 2 it will be noted that each has apivotal rod 25 to control movement of a selector latch, designated L,out of the path of a common actuating bail 26. Each latch interposer isnormally urged in a rearward direction by a spring 25', and eachselector latch is biased rearwardly into the path of the bail 26 by aspring 27. The actuating bail 26 is caused to be moved downwardlyagainst those selector latches L not removed from its path by the latchinterposers 24, and those latches engaged will operate through thedisplacement mechanism to advance the desired character, correspondingto the key lever depressed, into position for printing.

In order to correlate advancement of the actuating bail 26 with movementof the selector latches, each character interposer has a special lug 28which when depressed will strike a cycle ball 29 forcing the bail 29 tomove downwardly and, through suitable control linkage represented at 30,actuate a clutch member 32 for rotation of a cycle shaft 34 by motordrive 35. In each print cycle, the cycle shaft will rotate 180 andthrough gearing 36, 37 and 38 is operative to rotate a filter shaft 40through 180. The filter shaft 40 has diametrically opposed blades 41positioned beneath the character interposer so that in each 180 printcycle a blade on the filter shaft is engageable with the shoulder 42 onthe character interposer to advance the latter in a direction to engageand move one or more of the selector bails in the manner previouslydescribed.

As broadly illustrated in FIG. 2, the actuating bail 26 includes apivotal frame 43 having rollers 44 on either side which are biasedupwardly by a spring 45 into contact with cycle shaft cams, not shown,on the cycle shaft. As the cycle shaft is rotated through each printcycle the cams will engage the rollers 44 to force the bail to pivotdownwardly about its shaft causing displacement of those selectorlatches not moved out of position to actuate the displacement mechanism.Of course other parts and elements are associated with the characterselection unit described to insure proper correlation between theselector latches, actuating bail, cycle shaft and filter shaft in theprinting of each character, it being understood that the foregoingdescription of a typical keyboard printer unit is intended more as asetting for the following description of a preferred form of magneticswitch assembly.

As shown in FIGS. 2 to 5, the magnetic switch assembly 50 of the presentinvention comprises a plurality of magnetic actuating members 52, eachextending downwardly from connection to a latch interposer 24, and acorresponding number of reed'switches 54 are mounted on the back of aprinted circuit board 55 in alignment with the magnetic actuatingmembers. Broadly, each actuating member will follow forward advancementof its latch interposer in response to depression of a key lever toclose the associated reed switch and to cause a signal to be transmittedthrough suitable logical circuitry on the printed circuit board to arecording unit, not shown. Although forming no part of the presentinvention, a filter switch 56 mounted at the end of the filter shaft 40is operative to control the period of energization of a seriesofsolenoids 58 in automatically printing characters played back from therecording unit, all in a manner described in copending application forKeyboard Printer Character Selection Unit, filed .Ian. 21, 1969, Ser.No. 792,471. The filter switch may also be connected through a clockcircuit, not shown, to a suitable logic control circuit on the printedcircuit board 55 to synchronize the transmittal of each combination ofpulses representing a character in response to actuation of the reedswitches 54.

It is important to note that the reed switches 54 can be mounted on oneface of the printed circuit board opposite to the logic circuit elementsfor the keyboard printer unit so as to be in the direct path of movementof the magnetic actuating members 52. As shown in detail in FIGS. 4 and5, each reed switch conventionally comprises a glass envelope orcartridge 60 containing reed elements 61 and 62, and terminal leads 63and 64 extend from opposite ends of the cartridge for connection to theboard. Of course, various different types of reed switches arecommercially available, and as such the reed switch 54 forms no part ofthe present invention. For the purpose of illustration, however, thereed elements 61 and 62 may extend inwardly from opposite ends of thecartridge and be normally biased to an open or separated position. Thereeds are suitably composed of a magnetizable material so that when theinner free ends of the reeds are brought under the influence of amagnetic field the free ends will be drawn together to close the switchand form a path for transmission of a pulse from suitable pulsegenerating means in the logic circuit through the recording unit. Again,different forms of reed switches may be employed which in response tomovement of a magnetic actuating member into predetermined relation tothe inner ends of the reed elements will activate the pulse generatingcircuit for transmission of pulses to the recording unit, the importantfeature of the present invention residing more in the mounting andrelative disposition of the reed switch and magnetic actuating members.

In order to support each magnetic actuating member in predeterminedrelation to its respective switch, a holder is formed of a relativelythin flat strip composed of electrically nonconductive or nonmagneticmaterial possessing limited resiliency or flexibility, such as, aplastic or hard rubber or rubberlike material; and the strip is providedwith a recess 72 at one end for lateral insertion of a latch interposer24 and an open slot 74 at its opposite end for insertion of a bar magnet75. In the particular form shown, the cross-sectional dimension of thelatch interposer is relatively thin and narrow along the section orportion 76 just forwardly of the latch interposer spring 25'. In turn,the recess 72 is dimensioned to correspond in thickness and width tothat of the interposer portion 76 with a slot 78 of limited extentformed at the end of the interposer in communication with the recess andtransverse shoulder or abutment 79 extending partially across the end ofthe holder. As a result, and as viewed from the underside of the printerapparatus shown in FIG. 2, the slotted section 78 of the recess can belined up with the lower edge of the interposer portion 76 and the holder70 forced upwardly to cause the interposer portion 76 to advance intothe recess 72 until the upper edge of the interposer portion clears theterminal end 79 at which point the holder is snapped in place with thenatural tension of the sides of the holder surrounding the recess snuglyengaging the sides of the interposer portion 76. The open slot 74 formedalong the opposite end of the holder is relatively deep leaving aninterconnecting web portion 80 between the recess 72 and slot 74.Preferably the bar magnet is cylindrical in cross section with itsdiameter about twice the thickness of the interposer section 76 and, toestablish snug-fitting insertion of the magnet within the slot 74, theslot is provided with inwardly convergent sides forming inclinedsurfaces 82 extending inwardly from the end of the slot and terminatingin aligned grooves or depressions 84 to accommodate the magnet.Accordingly when the magnet is forced laterally and inwardly against theconvergent sides 82 it will cause the sides of the slot 74 to spreaduntil the magnet 75 is advanced into alignment with the grooves 84whereupon the sides of the slot will contract against the sides of themagnet to clamp it securely in place within the aligned grooves. It willbe further noted that the entrance to the slot as defined by theconvergent sides 82 is dimensioned along with the magnet 75 to bedisposed in surrounding, closely spaced relation to the external surfaceof the reed switch thereby forming a direct, closed magnetic path fromthe magnet 75 to the reed elements. Again, the magnet should be alignedwithin the holder in facing relation to the reed switch such that whenthe latch interposer is at rest and biased rearwardly the reed elementsare normally biased to an open position; but when the latch inter poseris advanced forwardly the magnet will pass across the free ends of thereed elements to close the switch.

In assembly, each of the magnet holders 70 is snapped in place on one ofthe latch interposers 24 and the magnets 74 are inserted within theslots 74 of the magnet holders. The printed circuit board 55 is thenmounted by suitable mounting brackets 88 and screws 89 to the frame Fand solenoid as sembly 58 of the printer unit with the reed switchesaligned, as shown in FIG. 3, with each of the respective magnets 75. Inthis connection, care should be taken in mounting of the printed circuitboard to insure that each magnet is arranged in closely spaced, parallelrelation to its reed switch, and further that the magnet is positionedand properly aligned within the slot so as to control opening andclosing of the reed switch in following the movement of the latchinterposer.

Once installed, the magnet holders can be adjusted with respect to thelatch interposers by positively forcing the holders along theinterposers in either direction, or the magnet may be adjusted withinthe slot by positively forcing the magnets in an axial direction fromeither end to obtain the desired alignment with the reed switches.Similarly the printed circuit board mounting brackets 88 will permit alimited degree of adjustment, aided if necessary by the use of shims, toeffect the desired alignment with the magnetic actuating members. As oneor more latch interposers 24 are advanced forwardly, against the urgingof their springs 25', the magnet holders 70 attached to the interposers24 will be correspondingly advanced with the magnets passing across thereed elements to cause each respective switch to close. The combinationof reed switches closed is therefore the same as the combination ofinterposers advanced by the selector bails 20. Accordingly, eachcombination of signals produced in response to depression of a key leveris representative of the chosen character and, when transmitted back tothe solenoid assembly 58 will cause actuation of the same latchinterposers 24 to automatically print the same character. Of course thelatch interposers are returned to their original disposition at or nearthe end of each print cycle to reopen the switches in preparation of thenext cycle.

Accordingly it will be seen that the magnetic switch assembly ischaracterized by its ease of installation with snap-on assembly of theholder and magnets and the magnets being held securely in place by thenatural resiliency of the holder material; yet the assembly permits easeof adjustment. Further, the holder will snugly engage the latchinterposer under its natural tension, although if desired the holder maybe adhesively secured or bonded to the interposer and any necessaryadjustment made through adjustment of the mag net. Moreover, theconvergent surfaces at the entrance to the slot for the magnet willcooperate in maintaining alignment between the magnet and reed switch aswell as to establish a closed magnetic path between the elements.Finally the parts comprising the switch assembly are low in cost andcharacterized by simplicity of mounting both of the reed switches on thecircuit board and of the holders on the latch interposers so as tooccupy a minimum of space.

It is to be understood from the foregoing that various modifications andchanges may be made in the construction and arrangement of elementscomprising the preferred form of present invention, particularly for usein other forms of printer apparatus than that described, withoutdeparting from the spirit of the present invention.

What is claimed is:

1. In a code generating keyboard system, a magnetic switch assembly forconverting translational movement of an elongated link arm to anelectrical signal comprising:

electrical signal generating means including a magnetically responsiveswitch member positioned in adjacent, spaced parallel relation to thelink arm and including switch elements movable between an open andclosed position in response to passage of the magnetic field of a magnetmoving parallel to the switch elements,

an elongated magnet to control movement of said switch member betweenthe open and closed positions, and

a magnet holder releasably connecting said elongated magnet to the linkarm, said holder provided with a recessed portion adjacent to one endthereof including an entrance opening through said holder for releasableinsertion of the link arm into the recessed portion in a directiontransversely of the length of the link arm, and said magnet beingreleasably inserted into a magnet-receiving slot at the end of saidholder opposite to the one end thereof in a direction transversely ofthe length of the link arm so as to be positioned parallel both to thelink arm and the switch member whereby to control movement of saidswitch member between the open and closed positions in response tolengthwise movement of the link arm in a direction parallel to theswitch member, and the magnetreceiving slot in said magnet holderdefined by opposed clamping side portions having forwardly divergent endportions diverging forwardly toward said switch member in a directionaway from the link arm, and said magnet being frictionally engaged bythe clamping side portions of said magnet holder, said clamping sideportions diverging toward the switch member with at least a portion ofthe switch member disposed in the slot between the forwardly divergentend portions in closely spaced, parallel relation to the magnet. I

2. In a code generating keyboard system according to claim 1, saidmagnet aligned in closed spaced parallel relation to said switch member,the polarity of the magnet being such as to close said switch element asthe magnet is advanced parallel to said switch element in response tomovement of the link arm.

3. In a code generating keyboard system according to claim 1, the linkarm-receiving recessed portion frictionally engaging the link arm andbeing slidable lengthwise of the link arm to align said magnet in themagnet-receiving slot in said magnet holder opposite to the switchmember, and said magnet being slidable in the magnet-receiving slot in adirection parallel to the length of the link arm independently ofslidable adjustment of said holder lengthwise of the link arm.

4. In a code generating keyboard unit having a plurality of interposersaligned in side-by-side relation to one another for lengthwise,independent movement of selected ones of said interposers between aninactive position and an active position according to a preselected codein advancing characters on the keyboard to a printing position, thecombination therewith comprising:

means for generating electrical signals representative of each characterselected in response to movement of selected ones of said interposersincluding a plurality of electrical switch members, each disposedopposite to one of said interposers and each including switch elementsmovable between an open and closed position in response to passage ofthe magnetic field of a magnet moving parallel to the switch member,

an elongated magnet for each of said switch members, and

a magnet holder releasably connecting each magnet to an interposer formovement of the magnet axially of its length in spaced parallel relationto its respective switch members in response to lengthwise movement ofan associated interposer, said magnet holder having opposed clampingside portions provided with forwardly divergent end portions divergingforwardly toward its associated switch member in a direction away fromsaid interposers to define an open slot therebetween for insertion ofsaid magnet in a direction transversely of the link arm, and said magnetbeing frictionally held in the slot by the clamping side portions inclosely spaced parallel relation to its respective switch member with atleast a portion of the switch member disposed between the forwardlydivergent end portions whereby to activate said switch member inresponse to lengthwise movement of its interposer.

5. In a code generating keyboard unit according to claim 4, saidclamping side portions having opposed, facing magnetreceiving groovestherein, the width of the slot defined by said clamping side portionsbeing such that said magnet will spread the side portions as it isinserted into alignment with the grooves so as to be securely heldwithin the grooves under the natural tension of the side portions of theslot.

6. In a code generating keyboard unit wherein a printing mechanism isactuated by control linkage in response to depression of one of aplurality of key levers, each key lever representative of a differentcharacter to advance a print element corresponding to that characterinto position, the combination therewith comprising:

a plurality of interposers aligned in closed spaced, side-bysiderelation to one another and operatively interconnecting said key leverswith said control linkage, different selected combinations of saidinterposers being independently and longitudinally movable in responseto depression of each key lever according to a preselected code, andeach interposer including a relatively flat, elongated holder-mountingportion,

electrical signal generating means including a mounting board in spacedparallel relation to the holder-mounting portions on said interposers, aplurality of magnetically controllable switch members each positioned onsaid mounting board in alignment with and in facing relation to one ofsaid holder-mounting portions on an interposer, each switch memberincluding switch elements movable between an open and closed position inresponse to passage of the magnetic field of a magnet moving parallel tothe switch members,

an elongated magnet for each of said switch members,

a magnet holder for releasable connection of each of said magnets to theholder-mounting portion of an interposer to follow the movement thereof,each holder being formed of a thin, flat rectangular strip ofnonmagnetic material having a recessed portion adjacent to one end, therecessed portion corresponding to the cross-sectional size of theholder-mounting portion with a side entrance into said recessed portionfor insertion of said holdermounting portion in a direction transverselyof the length of the link arm into frictional engagement within saidmagnet holder, and

a magnet-receiving slot at the end opposite to the one end thereofdefined by opposed, clamping side portions having forwardly divergentend portions diverging forwardly toward an associated switch member in adirection away from said interposers to define an open slot therebetweenfor insertion of said magnet into the slot in a direction transverselyof the interposer, the width of the slot defined by said clamping sideportions being such that said magnet will spread the side portions as itis inserted into the slot so as to be frictionally held within the slot,said clamping side portions diverging toward the switch member with atleast a portion of the switch member disposed in the slot between theforwardly divergent end portions in closely spaced, parallel relation tothe magnet, and said switch member being advanced between open andclosed positions when the magnet is moved in response to lengthwisemovement of its associated interposer.

1. In a code generating keyboard system, a magnetic switch assembly forconverting translational movement of an elongated link arm to anelectrical signal comprising: electrical signal generating meansincluding a magnetically responsive switch member positioned inadjacent, spaced parallel relation to the link arm and including switchelements movable between an open and closed position in response topassage of the magnetic field of a magnet moving parallel to the switchelements, an elongated magnet to control movement of said switch memberbetween the open and closed positions, and a magnet holder releasablyconnecting said elongated magnet to the link arm, said holder providedwith a recessed portion adjacent to one end thereof including anentrance opening through said holder for releasable insertion of thelink arm into the recessed portion in a direction transversely of thelength of the link arm, and said magnet being releasably inserted into amagnet-receiving slot at the end of said holder opposite to the one endthereof in a direction transversely of the length of the link arm so asto be positioned parallel both to the link arm and the switch memberwhereby to control movement of said switch member between the open andclosed positions in response to lengthwise movement of the link arm in adirection parallel to the switch member, and the magnetreceiving slot insaid magnet holder defined by opposed clamping side portions havingforwardly divergent end portions diverging forwardly toward said switchmember in a direction away from the link arm, and said magnet beingfrictionally engaged by the clamping side portions of said magnetholder, said clamping side portions diverging toward the switch memberwith at least a portion of the switch member disposed in the slotbetween the forwardly divergent end portions in closely spaced, parallelrelation to the magnet.
 2. In a code generating keyboard systemaccording to claim 1, said magnet aligned in closed spaced parallelrelation to said switch member, the polarity of the magnet being such asto close said switch element as the magnet is advanced parallel to saidswitch element in response to movement of the link arm.
 3. In a codegenerating keyboard system according to claim 1 the link arm-receivingrecessed portion frictionally engaging the link arm and being slidableLengthwise of the link arm to align said magnet in the magnet-receivingslot in said magnet holder opposite to the switch member, and saidmagnet being slidable in the magnet-receiving slot in a directionparallel to the length of the link arm independently of slidableadjustment of said holder lengthwise of the link arm.
 4. In a codegenerating keyboard unit having a plurality of interposers aligned inside-by-side relation to one another for lengthwise, independentmovement of selected ones of said interposers between an inactiveposition and an active position according to a preselected code inadvancing characters on the keyboard to a printing position, thecombination therewith comprising: means for generating electricalsignals representative of each character selected in response tomovement of selected ones of said interposers including a plurality ofelectrical switch members, each disposed opposite to one of saidinterposers and each including switch elements movable between an openand closed position in response to passage of the magnetic field of amagnet moving parallel to the switch member, an elongated magnet foreach of said switch members, and a magnet holder releasably connectingeach magnet to an interposer for movement of the magnet axially of itslength in spaced parallel relation to its respective switch members inresponse to lengthwise movement of an associated interposer, said magnetholder having opposed clamping side portions provided with forwardlydivergent end portions diverging forwardly toward its associated switchmember in a direction away from said interposers to define an open slottherebetween for insertion of said magnet in a direction transversely ofthe link arm, and said magnet being frictionally held in the slot by theclamping side portions in closely spaced parallel relation to itsrespective switch member with at least a portion of the switch memberdisposed between the forwardly divergent end portions whereby toactivate said switch member in response to lengthwise movement of itsinterposer.
 5. In a code generating keyboard unit according to claim 4,said clamping side portions having opposed, facing magnet-receivinggrooves therein, the width of the slot defined by said clamping sideportions being such that said magnet will spread the side portions as itis inserted into alignment with the grooves so as to be securely heldwithin the grooves under the natural tension of the side portions of theslot.
 6. In a code generating keyboard unit wherein a printing mechanismis actuated by control linkage in response to depression of one of aplurality of key levers, each key lever representative of a differentcharacter to advance a print element corresponding to that characterinto position, the combination therewith comprising: a plurality ofinterposers aligned in closed spaced, side-by-side relation to oneanother and operatively interconnecting said key levers with saidcontrol linkage, different selected combinations of said interposersbeing independently and longitudinally movable in response to depressionof each key lever according to a preselected code, and each interposerincluding a relatively flat, elongated holder-mounting portion,electrical signal generating means including a mounting board in spacedparallel relation to the holder-mounting portions on said interposers, aplurality of magnetically controllable switch members each positioned onsaid mounting board in alignment with and in facing relation to one ofsaid holder-mounting portions on an interposer, each switch memberincluding switch elements movable between an open and closed position inresponse to passage of the magnetic field of a magnet moving parallel tothe switch members, an elongated magnet for each of said switch members,a magnet holder for releasable connection of each of said magnets to theholder-mounting portion of an interposer to follow the movement thereof,each holder being formeD of a thin, flat rectangular strip ofnon-magnetic material having a recessed portion adjacent to one end, therecessed portion corresponding to the cross-sectional size of theholder-mounting portion with a side entrance into said recessed portionfor insertion of said holder-mounting portion in a directiontransversely of the length of the link arm into frictional engagementwithin said magnet holder, and a magnet-receiving slot at the endopposite to the one end thereof defined by opposed, clamping sideportions having forwardly divergent end portions diverging forwardlytoward an associated switch member in a direction away from saidinterposers to define an open slot therebetween for insertion of saidmagnet into the slot in a direction transversely of the interposer, thewidth of the slot defined by said clamping side portions being such thatsaid magnet will spread the side portions as it is inserted into theslot so as to be frictionally held within the slot, said clamping sideportions diverging toward the switch member with at least a portion ofthe switch member disposed in the slot between the forwardly divergentend portions in closely spaced, parallel relation to the magnet, andsaid switch member being advanced between open and closed positions whenthe magnet is moved in response to lengthwise movement of its associatedinterposer.